Image processing circuit and associated image processing method

ABSTRACT

The present invention provides an image processing circuit, wherein the image processing circuit comprises a receiving circuit, an image dividing circuit, a first image enlargement circuit, a second image enlargement circuit and an output circuit. In the operations of the image processing circuit, the receiving circuit receives image data, the image dividing circuit divides a pixel value of each pixel of the image data into two parts to generate first image data and second image data, the first image enlargement circuit enlarges the first image data in a linear manner to generate enlarged first image data, the second image enlargement circuit enlarges the second image data in a non-linear manner to generate enlarged second image data, and the output circuit generates an output image according to the enlarged first image data and the enlarged second image data.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to image processing, and moreparticularly, to an image enlargement techniques.

2. Description of the Prior Art

In a conventional image enlargement technique, a spline method is usedto calculate pixel values of the enlarged image. However, this methodcauses an irregular shape of the oblique edges in the image, and ifother image enlargement techniques are to be used to alleviate thisphenomenon, a large amount of computation is usually required toincrease the software operation time or the hardware manufacturing cost.In addition, when the enlargement factor (i.e. enlargement ratio) islarge, the enlarged image has a fuzzy edge transition at the edge, sothat a large amount of calculation is required to improve this issue.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide animage processing circuit, which can use a lower amount of computation togenerate the enlarged image with higher sharpness, to solve theabove-mentioned problems.

In one embodiment of the present invention, an image processing circuitis disclosed, wherein the image processing circuit comprises a receivingcircuit, an image dividing circuit, a first image enlargement circuit, asecond image enlargement circuit and an output circuit. In theoperations of the image processing circuit, the receiving circuitreceives image data, the image dividing circuit divides a pixel value ofeach pixel of the image data into two parts to generate first image dataand second image data, the first image enlargement circuit enlarges thefirst image data in a linear manner to generate enlarged first imagedata, the second image enlargement circuit enlarges the second imagedata in a non-linear manner to generate enlarged second image data, andthe output circuit generates an output image according to the enlargedfirst image data and the enlarged second image data.

In another embodiment of the present invention, an image processingmethod comprises the steps of: receiving image data; dividing a pixelvalue of each pixel of the image data into two parts to generate firstimage data and second image data; enlarging the first image data in alinear manner to generate enlarged first image data; enlarging thesecond image data in a non-linear manner to generate enlarged secondimage data; and generating an output image according to the enlargedfirst image data and the enlarged second image data.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an image processing circuit accordingto one embodiment of the present invention.

FIG. 2 shows the operations of the second image enlargement circuitaccording to one embodiment of the present invention.

FIG. 3 is a flowchart of an image processing method according to oneembodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating an image processing circuit 100according to one embodiment of the present invention. As shown in FIG.1, the image processing circuit 100 comprises a receiving circuit 110,an image dividing circuit 120, a first image enlargement circuit 130, asecond image enlargement circuit 140 and an output circuit 150. In thisembodiment, the image processing circuit 100 is used to receive imagedata (e.g. image frame) Din and perform the enlargement operations uponthe image data Din to generate an output image Dout, and the outputimage Dout is processed by a backend processing circuit 102 and thentransmitted to a display panel 104 to be displayed thereon.

In the operations of the image processing circuit 100, the receivingcircuit 110 receives the image data Din, and the image dividing circuit120 divides a pixel value of each pixel of the image data Din into twoparts to generate first image data Din1 and second image data Dint.Then, the first image enlargement circuit 130 enlarges the first imagedata Din1 in a linear manner to generate enlarged first image dataDin1′, and the second image enlargement circuit 140 enlarges the secondimage data Dint in a non-linear manner to generate enlarged second imagedata Din2′. Then, the output circuit 150 generates the output image Doutaccording to the enlarged first image data Din1′ and the enlarged secondimage data Din2′.

In the following descriptions, it is assumed that the image data Dincomprises consecutive N pixels in the same column or the same row of aframe. For convenience of explanation, the following contents aredescribed by using four consecutive pixels. Assuming that the pixelscorresponding to positions 0, 1, 2 and 3 of the image data Din have thepixel values “0”, “3”, “7” and “8”, respectively, and because the pixelvalues “0”, “3”, “7” and “8” are strict increasing sequence, the imagedividing circuit 120 can calculate the pixel value difference of eachpair of adjacent pixels of the four pixels to obtain three pixel valuedifferences, and refer a minimum one of the three pixel valuedifferences (the minimum pixel value difference can also be called ascommon brightness difference) to determine four first pixel values ofthe first image data Din1 and four second pixel values of the secondimage data Dint. Specifically, refer to table 1 as follows:

TABLE 1 Position 0 1 2 3 Original pixel value 0 3 7 8 Pixel valuedifference 3 4 1 Minimum pixel value difference 1 1 1 First pixel value0 1 2 3 Second pixel value 0 2 5 5

In the Table 1, because the minimum pixel value difference is equal to“1”, the image dividing circuit 120 uses the minimum pixel valuedifference to calculate an equally spaced sequence 0, 1, 2, 3 as thefirst pixel values in the first image data Din1, and these first pixelvalues are determined to be suitable for using the linear interpolationto enlarge the image. In addition, the image dividing circuit 120subtracts the first pixel values 0, 1, 2 and 3 from the four originalpixel values 0, 3, 7 and 8 to obtain four second pixel values 0, 2, 5and 5, and the second pixel values are determined to be unsuitable forusing the linear interpolation to enlarge the image.

In the operations of the first image enlargement circuit 130, the firstpixel values 0, 1, 2, and 3 are linearly interpolated to generate(3*M+1) pixel values of the enlarged first image data Din1′, where M isan enlargement factor. In Table 2 shown below, the enlargement factor is“10” as an explanation.

In the operations of the second enlargement circuit 140, referring toFIG. 2, the second image enlargement circuit 140 first calculates acenter pixel value of a transition zone of the four second pixel values0, 2, 5 and 5. In this embodiment, the four second pixel values 0, 2, 5and 5 themselves can be regarded as the transition zone, and the pixelvalues 0 and 5 are respectively used as two end values of the transitionzone, and the second enlargement circuit 140 can calculate an average ofthe end values of the transition zone (i.e., 0 and 5) to obtain thecenter pixel value “2.5” of the transition zone. Then, the second imageenlargement circuit 140 calculates (3*M+1) pixel values in the enlargedsecond image data Dint′ according to a set slope, wherein as shown inFIG. 2, the (3*M+1) pixel values of the enlarged second image data Dint′contain three segments, wherein each pixel value of the leftmost firstsegment is equal to the end value “0” of the transition zone. Theplurality of pixel values of the second segment are generated by usingthe two end values of the transition zone to perform the interpolationcalculation, and the plurality of pixel values of the second segmentpass at least the center pixel value of the transition zone, and in apreferred embodiment, the plurality of pixel values of the secondsegment also include one of the second pixel values (i.e. the secondpixel value “2”). Each pixel value of the rightmost third segment isequal to the end value “5” of the transition zone.

Finally, the output circuit 150 directly combines the (3*M+1) pixelvalues of the enlarged first image data Din1′ with the (3*M+1) pixelvalues of the enlarged second image data Dint′ to generate (3*M+1) pixelvalues of the output image Dout.

The Table 2 shows an example of the thirty-one (i.e. 3*10+1) pixelvalues in the enlarged first image data Din1′ (assuming that theenlargement factor is “10”), thirty-one pixel values in the enlargedsecond image data Din2′, and thirty-one pixel values in the output imageDout.

TABLE 2 Position 0 1 2 3 4 5 6 7 8 9 10 Enlarged 0 0.1 0.2 0.3 0.4 0.50.6 0.7 0.8 0.9 1 first image data Din1′ Enlarged 0 0 0 0 0 0 0 0.5 11.5 2 second image data Din2′ Output image 0 0.1 0.2 0.3 0.4 0.5 0.6 1.21.8 2.4 3 Position 10 11 12 13 14 15 16 17 18 19 20 Enlarged 1 1.1 1.21.3 1.4 1.5 1.6 1.7 1.8 1.9 2 first image data Din1′ Enlarged 2 2.5 33.5 4 4.5 5 5 5 5 5 second image data Din2′ Output image 3 3.6 4.2 4.85.6 6 6.6 6.7 6.8 6.9 7 Position 20 21 22 23 24 25 26 27 28 29 30Enlarged 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 first image data Din1′Enlarged 5 5 5 5 5 5 5 5 5 5 5 second image data Din2′ Output image 77.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8

The above embodiment is an enlargement operation of a plurality ofpixels having a single direction (for example, a lateral enlargementoperation of the image data Din), and then the image dividing circuit120, the first image enlargement circuit 130, and the second imageenlargement circuit 140 perform the enlargement operations upon thepixels in the other direction (for example, the longitudinal directionof the image data Din), to complete the enlargement of the entire imagedata Din to generate the output image Dout. Since the pixels at the edgeof the image generally have strict increasing/decreasing pixel values,the operations of the above embodiment can surely and effectively reducethe edge blur caused by the enlargement operations. In addition, becausethe calculation steps are relatively simple, only simple softwareoperations or hardware calculation circuits are required to reduce thedesign and manufacturing costs.

In an embodiment, if the pixel values corresponding to the positions 0,1, 2 and 3 of the image data Din are not increasing/decreasing sequenceor a strict increasing/decreasing sequence, for example, 2, 1, 4 and 3,the image dividing circuit 120 can divide the pixel values 2, 1, 4, 3 toobtain the first pixel value “2, 1, 1, 0” and the second pixel value “0,0, 3, 3”, to perform the linear interpolation operation and nonlinearinterpolation operation respectively, and then add together to obtainthe output image.

It should be noted that the enlargement operations of the pixel valuesin the above embodiment may include a plurality of pixel values ofdifferent colors according to different color models. Taking the “red,green and blue” color model as an example, the enlargement operations ofthe plurality of pixels includes the enlargement operations of red pixelvalues, green pixel values, and blue pixel values. Taking the “luminanceand color difference (YUV)” color model as an example, the enlargementoperations of the plurality of pixels includes the enlargementoperations brightness, blue chroma components, and red chromacomponents. Taking the “cyan, magenta, yellow, black (CMYK)” color modelas an example, the enlargement operations of the plurality of pixelsincludes cyan pixel values, magenta pixel values, yellow pixel valuesand black pixel values.

FIG. 3 is a flowchart of an image processing method according to oneembodiment of the present invention. Refer to the above disclosure, theflow of the image processing method is described as follows.

Step 300: the flow starts.

Step 302: receive image data.

Step 304: divide a pixel value of each pixel of the image data into twoparts to generate first image data and second image data.

Step 306: enlarge the first image data in a linear manner to generateenlarged first image data.

Step 308: enlarge the second image data in a non-linear manner togenerate enlarged first image data.

Step 310: generate an output image according to the enlarged first imagedata and the enlarged second image data, wherein the output image istransmitted to a display panel to be displayed thereon.

Briefly summarized, in the image processing circuit of the presentinvention, firstly, the image data is divided into the first image dataand the second image data, then the first image data and the secondimage data are processed by the linear interpolation operations and thenon-linear interpolation operations, respectively, to generate theenlarged first image data and the enlarged second image data, then theenlarged first image data and the enlarged second image data arecombined to generate the output image. By using the image processingcircuit of the present invention, the edge blur caused by theenlargement operations can be effectively reduced without increasing toomuch design and manufacturing costs.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An image processing circuit, comprising: areceiving circuit, arranged to receive image data; an image dividingcircuit, arranged to divide a pixel value of each pixel of the imagedata into two parts to generate first image data and second image data;a first image enlargement circuit, arranged to enlarge the first imagedata in a linear manner to generate enlarged first image data; a secondimage enlargement circuit, arranged to enlarge the second image data ina non-linear manner to generate enlarged second image data; and anoutput circuit, arranged to generate an output image according to theenlarged first image data and the enlarged second image data.
 2. Theimage processing circuit of claim 1, wherein for consecutive N pixels ofthe image data, the image dividing circuit divides original pixel valuesof the N pixels into two parts according to pixel value differences ofeach pair of adjacent pixels of the N pixels, to generate N first pixelvalues of the first image data and N second pixel values of the secondimage data.
 3. The image processing circuit of claim 2, wherein when theN original pixel values of the N pixels are strict increasing sequence,the image dividing circuit calculates the pixel value differences ofeach pair of adjacent pixels of the N pixels to generate (N−1) pixelvalue differences, and selects a minimum pixel value difference from the(N−1) pixel value differences to generate the N first pixel values,wherein each of pixel value differences of each pair of adjacent pixelsof the N first pixel values is equal to the minimum pixel valuedifference.
 4. The image processing circuit of claim 3, wherein theimage dividing circuit subtracts the N first pixel values from the Noriginal pixel values to generate the N second pixel values.
 5. Theimage processing circuit of claim 2, wherein the second imageenlargement circuit determines a first end value and a second end valueof a transition zone according to the N second pixel values, andcalculates a center pixel value of the transition zone; and the secondimage enlargement circuit refers to the first end value, the second endvalue and the center pixel value of the transition zone to enlarge the Nsecond pixel values in the non-linear manner to generate (N−1)*M+1 pixelvalues of the enlarged second image data, wherein M is an enlargementfactor.
 6. The image processing circuit of claim 5, wherein the(N−1)*M+1 pixel values comprises three segments, each of the pixelvalues of a first segment is equal to the first end value of thetransition zone, the pixel values of a second segment are calculated byusing interpolations according to the first end value and the second endvalue of the transition zone, and each of the pixel values of a thirdsegment is equal to the second end value of the transition zone.
 7. Theimage processing circuit of claim 6, wherein the pixel values of thesecond segment are calculated by using linear interpolations accordingto the first end value and the second end value of the transition zone.8. The image processing circuit of claim 7, wherein the pixel values ofthe second segment comprise the center pixel value of the transitionzone, and the center pixel value of the transition zone is an average ofthe first end value and the second end value of the transition zone. 9.The image processing circuit of claim 5, wherein the first imageenlargement circuit performs a linear interpolation operation upon the Nfirst pixel values to generate (N−1)*M+1 pixel values of the enlargedfirst image data, and the output circuit directly adds the (N−1)*M+1pixel values of the enlarged first image data and the (N−1)*M+1 pixelvalues of the enlarged second image data to generate the output image.10. An image processing method, comprising: receiving image data;dividing a pixel value of each pixel of the image data into two parts togenerate first image data and second image data; enlarging the firstimage data in a linear manner to generate enlarged first image data;enlarging the second image data in a non-linear manner to generateenlarged second image data; and generating an output image according tothe enlarged first image data and the enlarged second image data. 11.The image processing method of claim 10, wherein the step of dividingthe pixel value of each pixel of the image data into two parts togenerate the first image data and the second image data comprises: forconsecutive N pixels of the image data, dividing original pixel valuesof the N pixels into two parts according to pixel value differences ofeach pair of adjacent pixels of the N pixels, to generate N first pixelvalues of the first image data and N second pixel values of the secondimage data.
 12. The image processing method of claim 11, wherein thestep of dividing the pixel value of each pixel of the image data intotwo parts to generate the first image data and the second image datacomprises: when the N original pixel values of the N pixels are strictincreasing sequence, calculating the pixel value differences of eachpair of adjacent pixels of the N pixels to generate (N−1) pixel valuedifferences, and selecting a minimum pixel value difference from the(N−1) pixel value differences to generate the N first pixel values,wherein each of pixel value differences of each pair of adjacent pixelsof the N first pixel values is equal to the minimum pixel valuedifference.
 13. The image processing method of claim 12, wherein thestep of dividing the pixel value of each pixel of the image data intotwo parts to generate the first image data and the second image datacomprises: subtracting the N first pixel values from the N originalpixel values to generate the N second pixel values.
 14. The imageprocessing method of claim 11, wherein the step of enlarging the secondimage data in the non-linear manner to generate the enlarged secondimage data comprises: determining a first end value and a second endvalue of a transition zone according to the N second pixel values;calculating a center pixel value of the transition zone; and referringto the first end value, the second end value and the center pixel valueof the transition zone to enlarge the N second pixel values in thenon-linear manner to generate (N−1)*M+1 pixel values of the enlargedsecond image data, wherein M is an enlargement factor.
 15. The imageprocessing method of claim 14, wherein the (N−1)*M+1 pixel valuescomprises three segments, each of the pixel values of a first segment isequal to the first end value of the transition zone, the pixel values ofa second segment are calculated by using interpolations according to thefirst end value and the second end value of the transition zone, andeach of the pixel values of a third segment is equal to the second endvalue of the transition zone.
 16. The image processing method of claim15, wherein the pixel values of the second segment are calculated byusing linear interpolations according to the first end value and thesecond end value of the transition zone.
 17. The image processing methodof claim 16, wherein the pixel values of the second segment comprise thecenter pixel value of the transition zone, and the center pixel value ofthe transition zone is an average of the first end value and the secondend value of the transition zone.
 18. The image processing method ofclaim 14, wherein the step of enlarging the first image data in thelinear manner to generate the enlarged first image data comprises:performing a linear interpolation operation upon the N first pixelvalues to generate (N−1)*M+1 pixel values of the enlarged first imagedata; and directly adding the (N−1)*M+1 pixel values of the enlargedfirst image data and the (N−1)*M+1 pixel values of the enlarged secondimage data to generate the output image.